Is it hooked up to vacuum on the carb body, or vacuum on the manifold? What is the procedure to set idle mixture on a 2bbl with the vac gauge?

 

You want full manifold vacuum so don't come off the vacuum going to the distributor. I had an unused port towards the front of my manifold that I was able to use but my engine has had most of the vacuum stuff pulled off of it. You may have to "T" off one of the manifold vacuum ports like the one that feeds the PCV. Someone else here may have a better way to do it but that's what comes to mind.

Here's what I did. First I used the vac gauge to set the distributor timing again. I've got an automatic transmission and no AC so I have the curb idle at about 850 rpm in neutral which winds up about 600 rpm in drive. I pulled the vac advance hose off the distributer and plugged it using an old golf tee. Then I loosened the distributor and advanced it for maximum vacuum (Hg) and then backed it off (retarded the timing) 1 Hg for ping. I checked it with the timing light afterwards and it looks like it was darn close the way I had it. Spec on my year of engine is 14° btdc, but I need a little more at my altitude. I'd previously set it using the timing light only at about 18° btdc, but after using the vac gauge I was at 16° btdc. I like using the vac gauge to set the timing as the motor is telling me where it wants to be rather than me setting it to a given spec.

Then I tweaked the idle mix screws. I leaned each to where vac started to drop off, then back towards rich to the point where the Hg readings just came back up but NO further. I didn't add any extra 1/8 or 1/4 turns. Just left it where it was.

All my vac readings were steady. Overall top vac reading was about 19 Hg when I had the distributor timing maxed out, then final setting at 18 Hg after retarding 1 Hg for ping. The vac reading remained there after the idle mix tweaks. According to the instructions in the gauge package it's calibrated for sea level, and you need to add 1 Hg for every 1000' above sea level you are. If that's correct, then actual peak vac reading was 24 Hg, and final set point was 23 Hg.

This is what worked best on mine, hope it helps.

Stan

 

Thanks for the timing vac setting> I have always used vac to set the mix setting. It never fails.